CN109937101B

CN109937101B - Locating sensor data collected during additive manufacturing

Info

Publication number: CN109937101B
Application number: CN201780070313.6A
Authority: CN
Inventors: 凯里·布朗; 约翰·黛尔迪丝; A·C·诺尔曼
Original assignee: Renishaw PLC
Current assignee: Renishaw PLC
Priority date: 2015-11-16
Filing date: 2017-11-10
Publication date: 2022-06-10
Anticipated expiration: 2037-11-10
Also published as: US20220203451A1; CN108349005A; JP2018536092A; WO2017085468A1; ES2948448T3; US11305354B2; CN114309670A; EP3377252A1; US20180370144A1; CN108349005B; US20210146447A1; CN109937101A; EP3377251A1; US10933468B2; GB201707807D0; CN108290219B; CN108290219A; US20190022946A1; WO2017085469A1; JP2018536560A

Abstract

The invention relates to a method of monitoring an additive manufacturing process in which an object (103) is built in a layer-by-layer manner by directing a laser beam (118a, 118b) using at least one movable guiding element (150a, 150b) of a scanner (157a, 157b) to solidify a selected region of a material bed. The method comprises the following steps: recording a position value (thetan,

) (ii) a Recording sensor values (S) generated by sensors (161a, 161b) for detecting radiation_n) The radiation emitted from the material bed and transmitted to a sensor (161a, 161b) by a movable guiding element (150a, 150b) of the scanner (157a, 157 b); and comparing each sensor value (S)_n) And the position value (on,

) Is associated with a corresponding one of the position values.

Description

Locating sensor data collected during additive manufacturing

Technical Field

The present invention relates to an apparatus and method for locating sensor data collected by an optical system of an optical scanner of an additive manufacturing apparatus (such as a powder bed melting apparatus) to a location in the additive manufacturing apparatus and/or an object manufactured using the additive manufacturing apparatus.

Background

Additive manufacturing or rapid prototyping processes for producing parts include layer-by-layer solidification of flowable materials. There are a number of different additive manufacturing methods, including material bed systems, such as Selective Laser Melting (SLM), Selective Laser Sintering (SLS), and stereolithography systems.

In selective laser melting, a powder layer is deposited on a powder bed in a build chamber, and a laser beam is scanned across portions of the powder layer corresponding to a cross-section (a slice) of the object being constructed. The laser beam melts or sinters the powder to form a solidified layer. After selective curing of the layers, the powder bed reduces the thickness of the newly cured layer and another layer of powder is spread over the surface and cured as needed. In a single build, more than one object may be built, with the parts spaced apart in the powder bed.

The laser beam is scanned over the powder bed, typically using an optical scanner comprising a pair of tilted mirrors, each of which is rotated under the control of a galvanometer. The transducer is arranged to measure the position of the tilting mirror/galvanometer to control the tilting mirror position. In this way, the required position can be achieved.

WO 2007/147221 a1 discloses a selective laser melting device comprising a scanner for scanning a laser beam across the powder surface, and a spatially resolved detector (e.g. a CCD or CMOS camera) or an integrated detector (e.g. a photodiode with a large active area) for capturing radiation emitted by the melting zone and transmitted through the optical system of the scanner.

US 2013/0168902 a1 discloses a method for producing three-dimensional components by means of a laser melting process, in which sensor values captured using the device disclosed in WO 2007/147221 a1 are stored together with coordinate values which position the sensor values in the component, and the detected positions with respect to the sensor values in the component are displayed in a two-and/or multi-dimensional representation by means of a visualization unit.

The sensor values can be located to the coordinate values using build coordinate values (so-called "demand data" -basic information of the build process). However, due to delays in transmitting the demand signal, inertia of the tilting mirror, noise in the system interfering with the demand signal, etc., there may be a difference between the demanded position of the tilting mirror of the scanner and the actual position of the tilting mirror at the time of capturing the sensor values, which may result in inaccurate positioning of the sensor data.

Alternatively, area capture of the powder bed may be used to locate the sensor values to coordinate values. However, cameras with sufficient resolution and frame rate to obtain the required positional accuracy of the melt zone are either prohibitively expensive or, for large beds, impractical with existing techniques.

Disclosure of Invention

According to a first aspect of the invention there is provided a method of monitoring an additive manufacturing process in which an object is built in a layer-by-layer manner by directing a laser beam using at least one movable guiding element of a scanner to solidify selected regions of a bed of material, the method comprising: recording a position value produced by a transducer measuring the position of the at least one movable guide element; recording sensor values generated by a sensor for detecting radiation emitted from the material bed and transmitted to the sensor by a movable guiding element of the scanner; and associating each sensor value with a corresponding one of the position values.

In this way, sensor values may be positioned in the object and/or the material bed based on the measured position of the movable guiding element. This may avoid inaccuracies in sensor positioning that may occur when using a demand location or area capture of the material bed to position sensor values. In addition, a transducer for measuring the position of the movable guide element of the scanner is typically provided for controlling the positioning of the movable guide element, thereby eliminating the need for additional devices (such as high resolution, fast frame rate cameras) to determine the capture position of the sensor value. Measuring the temperature of the material bed, the melt pool size, shape or other dimensions, the melt pool temperature, etc. may not be sufficient to validate the additive manufacturing process. Furthermore, in order to validate an additively built object, it is important to know accurately whether a melted/solidified area has been formed at the desired location. The invention enables such a position to be determined from a position value generated by a transducer measuring the position of the at least one movable guiding element. The at least one movable guide element may comprise: a first movable guide element for guiding the laser beam in a first dimension; and a second movable guiding element for guiding the laser beam to a second dimension substantially perpendicular to the first dimension, the method comprising: recording a first position value produced by a first transducer measuring the position of the first movable guide element; recording a second position value produced by a second transducer measuring the position of the second movable guide element; and associating each sensor value with a corresponding one of the first position value and the second position value.

The additive manufacturing process may comprise guiding the laser beam using a further movable guiding element, the further movable guiding element guiding the laser beam to the same dimension as the at least one movable guiding element, the method comprising: recording a further position value generated by a further transducer measuring the position of the further movable guide element; and associating each sensor value with a corresponding one of the further position values. For example, the further movable guiding element may be for guiding the laser beam to the first dimension or the second dimension. The further movable guiding element may provide a faster dynamic response but a smaller range of movement of the laser beam than the at least one movable guiding element. For example, the scanner may be a scanner as described in WO 2016/156824, which document is incorporated herein by reference.

The at least one movable guiding element may be one or more tiltable mirrors. The or each tiltable mirror can be moved under the control of an actuator, such as a galvanometer. The transducer may measure the angular position of the or each tiltable mirror.

Alternatively or additionally, the movable guiding element may be an optical element, such as at least one mirror, which is mounted to be movable on the gantry system such that the optical element is capable of guiding the laser beam to different areas of the material bed. The transducer can measure the position of the optical element on the gantry.

The further guiding element may be one or more further tiltable mirrors. Each further tiltable mirror can be moved under the control of an actuator, such as a piezo-electric actuator. The further transducer may measure the angular position of the further tiltable mirror.

Associating each sensor value with a corresponding one of the location values may include associating the sensor value and the corresponding one of the location values with a common identifier. The common identifier may be a time, such as a time associated with a demand signal directing the scanner to move the laser beam to a position on the material bed, and/or a time derived from a clock signal.

Associating each sensor value with a corresponding one of the location values may include packaging the sensor value and the corresponding one of the locations in a single data packet.

The method may comprise positioning the sensor value in the object and/or in the additive manufacturing apparatus based on the measured position of the movable guiding element. Locating the sensor values in the object may include locating the sensor values in a coordinate reference frame of the object. Positioning sensor values in the additive manufacturing apparatus may comprise positioning sensor values in a coordinate reference system of the material bed. (the material bed typically moves with the movement of the build platform in the additive manufacturing apparatus. thus, the coordinate reference system of the material bed may not be fixed relative to other elements of the apparatus, such as the scanner). Positioning the sensor values in the additive manufacturing apparatus may comprise positioning the sensor values in a coordinate reference system of the scanner, such as a polar reference system of a tiltable mirror or a cartesian coordinate reference system of a gantry. Where the scanner comprises a combination of tiltable mirrors movable in a gantry system, the method can comprise positioning the sensor values in a coordinate reference system fixed relative to the axis of rotation(s) of the tiltable mirror(s).

The method can comprise the following steps: the sensor values are displayed in a multi-dimensional representation with respect to the position of the sensor values in the object and/or the material bed. The multi-dimensional representation may include a two-dimensional, three-dimensional, and/or four-dimensional representation of the sensor data in the object and/or the material bed.

The method can comprise the following steps: the signals from the transducer are shielded from external noise and/or the scanner's demand signals. The transducer may generate an analog signal and the method may include shielding the analog signal from external noise and/or the demand signal until the analog signal is converted to a digital signal.

The transducer may produce an analog signal and the method may include filtering the analog signal to filter out noise before the analog signal is converted to a digital signal.

According to a second aspect of the invention, there is provided a scanner for an additive manufacturing apparatus in which an object is built in a layer-by-layer manner, the scanner comprising: at least one guide element for guiding a laser beam to cure a selected region of the material bed; a transducer for measuring the position of the at least one movable guide element; a light path having an output for directing light towards a sensor for detecting radiation emitted from the material bed and transmitted to the output by the movable guiding element; and an interface for outputting from the scanner a position signal generated by the transducer.

In this way, the actual position of the movable guide element can be read from the scanner and used, for example, for positioning sensor values in the object and/or the material bed.

The at least one movable guide element may comprise: a first movable guiding element for guiding the laser beam to a first dimension; a second movable directing element for directing the laser beam to a second dimension substantially perpendicular to the first dimension, and the interface for outputting a first position signal generated by the first transducer and a second position signal generated by the second transducer.

The scanner may include directing the laser beam using a further movable directing element that directs the laser beam to the same dimension as the at least one movable directing element, and the interface is to output a further position signal generated by the further transducer. The further movable guiding element may be for guiding the laser beam to the first dimension or the second dimension. The further movable guiding element may provide a faster dynamic response but a smaller range of movement of the laser beam than the at least one movable guiding element. For example, the scanner may be a scanner as described in WO 2016/156824, which document is incorporated herein by reference.

The at least one movable guiding element may be one or more tiltable mirrors. The or each tiltable mirror can be moved under the control of an actuator, such as a galvanometer. The transducer may measure the angular position of the or each tiltable mirror. The transducer may conform to the position detector described in US 5844673. Alternatively, the transducer can measure the position of the tiltable mirror directly rather than by axial position. For example, the transducer may comprise a laser that directs a laser beam in front of or behind a tiltable mirror, and a detector for measuring the reflected laser beam. The intensity of the laser beam on the tiltable mirror can vary with the position of the mirror. Measuring the mirror position in this manner may eliminate hidden modes associated with shaft torsion.

The further guiding element may be one or more further tiltable mirrors. Each additional tiltable mirror can be moved under the control of an actuator (e.g., a piezoelectric actuator). The further transducer may measure the angular position of the further tiltable mirror. The transducer may be as described above with respect to the one or more tiltable mirrors.

The light path including the at least one movable guiding element may be accommodated within a light-tight housing.

The interface may shield the output of the position signal from external sources having electromagnetic interference and/or from electromagnetic interference generated by the demand signal.

The interface may further provide an input for a demand signal for controlling the position of the movable guide element. The interface may include an output line for the position signal and an input line for the demand signal, and a shield for shielding each of the input line and the output line from electromagnetic interference generated by the other of the input circuit and the output circuit. The input line and the output line may be provided as different layers of a printed circuit board, wherein the input line and the output line are separated by a ground plane to shield each of the input line and the output line from electromagnetic interference generated by signals in the other of the input line and the output line.

The scanner may further comprise processing circuitry for processing the position signal. The transducer may generate an analog position signal and the processing circuitry includes an analog-to-digital converter for converting the analog position signal to a digital position signal. Digital position signals are more resistant to interference than analog signals. The processing circuit may further include a filter for filtering noise from the position signal. The processing circuitry may be housed within a housing for shielding the processing circuitry from external electromagnetic interference.

Due to the required accuracy for locating the position values of the sensor values and the significant electromagnetic noise generated by the additive manufacturing apparatus, it may be important to shield the position signals from interference when outputting position signals having the required accuracy.

According to a third aspect of the invention there is provided an additive manufacturing apparatus in which an object is built in a layer-by-layer manner, the additive manufacturing apparatus comprising a scanner according to the second aspect of the invention.

The additive manufacturing apparatus may be arranged to perform the method of the first aspect of the invention.

According to a fourth aspect of the invention there is provided a method of identifying the position of an area captured by a sensor in an object or an additive manufacturing apparatus during an additive manufacturing process in which an object is built in a layer-by-layer manner by directing a laser beam using at least one movable guiding element of a scanner to cure a selected area of a material bed, the sensor being arranged to detect radiation emitted from the material bed and transmitted to the sensor by the movable guiding element, the method comprising: receiving a sensor value generated by the sensor; receiving position values generated by transducers measuring the position of the at least one movable guide element, each sensor value being associated with a corresponding one of the position values; and for each sensor value, determining a location position in the object and/or the additive manufacturing apparatus of a region from which the sensor value was generated during the additive manufacturing process.

The method may comprise displaying the sensor values in a multi-dimensional representation with respect to their position in the object and/or the material bed. The multi-dimensional representation may include a two-dimensional, three-dimensional, and/or four-dimensional representation of the sensor data in the object and/or the material bed.

According to a fifth aspect of the invention, there is provided an apparatus comprising a processor arranged to perform the method of the fourth aspect of the invention.

The device may comprise a display for displaying the sensor values in a multi-dimensional representation.

According to a sixth aspect of the present invention there is provided a data carrier having instructions stored thereon, which when executed by a processor cause the processor to perform a method according to the fourth aspect of the present invention.

The data carrier may be a suitable medium for providing instructions to a machine, such as a non-transitory data carrier, e.g. a floppy disk, a CD ROM, a DVD ROM/RAM (including-R/-RW and + R/+ RW), a HD DVD, a Blu Ray (TM) optical disk, a Memory (such as a Memory Stick (TM), an SD card, a compact flash card, etc.), a disk drive (such as a hard disk drive), a magnetic tape, any magnetic/optical Memory; or a transitory data carrier such as a signal over a wire or fiber optic line or a wireless signal, e.g., a signal transmitted over a wired or wireless network (such as internet download, FTP transfer, etc.).

Drawings

Fig. 1 is a schematic view of an additive manufacturing apparatus according to an embodiment of the invention;

fig. 2 is a schematic view of the additive manufacturing apparatus shown in fig. 1 from another side; and is

FIG. 3 is a schematic diagram of the electronic components of a scanner according to an embodiment of the present invention;

fig. 4 is a schematic diagram of a system architecture of an additive manufacturing apparatus;

FIG. 5 is a schematic diagram of a build file according to one embodiment of the invention;

fig. 6 is a schematic diagram of a sub-command generated by a controller of an additive manufacturing apparatus;

FIG. 7 is a schematic diagram of reporting sensor data packets to a controller; and is

Fig. 8 is a schematic diagram of an outgoing data packet according to the present invention.

Detailed Description

Referring to fig. 1-3, an additive manufacturing apparatus according to an embodiment of the invention comprises a build chamber 101 having

baffles

115, 117 therein defining a build sleeve/cylinder 116 and a surface on which powder may be deposited. A build platform 102 is provided for supporting a workpiece 103 built by selective laser melting of powder 104. As successive layers of the workpiece 103 are formed, the platform 102 may be lowered within the build sleeve 116 under the control of the motor 119. The available build volume is defined by the extent to which the build platform 102 can be lowered into the build sleeve 116.

A powder layer is formed when the workpiece 103 is built by lowering the platform 102 and spreading the powder dispensed from the dispensing apparatus 108 apart using the wiper 109. The dispensing device 109 may be, for example, a device as described in WO 2010/007396. This produces a powder bed 104.

A plurality of laser modules (in this embodiment two

laser modules

105a, 105b) generate

laser light

118a, 118b for melting the powder 104, which

laser light

118a, 118b is directed according to the needs of the corresponding scanner (in this embodiment the

optical modules

106a, 106 b). The

laser beams

118a, 118b enter the chamber 101 through the window 107.

In this embodiment, the

laser modules

105a, 105b comprise fiber lasers, such as Nd YAG fiber lasers. The laser beam enters the optical module from above and is reflected towards a movable guiding mirror.

Each

optical module

106a, 106b includes a pair of movable guiding elements in the form of tiltable mirrors 150 (only one of which is shown for each

optical module

106a, 106 b). One of the

mirrors

150a, 150b is tiltable to steer the laser beam in the X direction, and the other of the

tiltable mirrors

150a, 150b is tiltable to steer the laser beam in the Y direction perpendicular to the X direction. The movement of each

tiltable mirror

150a, 150b is driven by

galvanometers

151, 152. The position of each galvanometer is measured by

transducers

153, 154. In this embodiment, the transducer is in accordance with the transducer described in US 5844673. Each

optical module

106a, 106b further includes movable focusing

optics

155a, 155b for adjusting the focal length of the corresponding laser beam.

The

beam splitters

156a, 156b direct light at the laser wavelength from the input to the

tiltable mirrors

150a, 150b and transmit light at other wavelengths emitted from the powder bed 104 to the in-

process monitoring modules

160a, 160 b. The in-

process monitoring module

160a, 160b comprises at least one

detector

161a, 161b for detecting the overall intensity and/or the spatial intensity of the transmitted light.

The optical elements of the scanner are housed in a light-

tight housing

157a, 157 b.

Referring to fig. 3 and 3b, a high voltage demand signal D for driving each

galvanometer

151, 152_x、D_yFrom the optical module controller 180 to the

galvanometers

151, 152. Low voltage analog position signal P from

transducers

153, 154_x、P_yAnd a sensor signal S from the detector 161_nIs sent to the optical module controller 180.

The optical module controller 180 comprises means for generating a demand signal D based on a control signal SC received from the main controller 140_x、D_yAnd for processing the sensor signal S from the in-process monitoring module 160 (described in more detail below)_nAnd position signals P from the

transducers

153, 154_x、P_yThe sensor processing circuit of (1). The processing circuit comprises a circuit for processing the analog position signal P_x、P_yFilter 182 for filtering and for converting an analog position signal to a digital signal theta _n、

The analog-to-digital converter 183. The circuitry is housed within a dust cover 181.

Demand signal D_x、D_yTransmitted to a galvanometer in a light-tight housing 157, and a position signal P_x、P_yTransmitted through the opaque housing through interface 170. The interface 170 provides shielding against the position signal P_x、P_yAnd a demand signal D_x、D_yCan be significantly interfered with each otherCan result in inaccurate position measurements and/or incorrect positioning of the mirror 150. In this embodiment, the interface comprises a PCB having a first layer 171 with a demand signal track for transmitting a demand signal and a second layer 172 with a position signal track for transmitting a position signal. The two

layers

171, 172 are separated by another layer having a ground plane 173 between the demand signal track and the location signal track to shield each signal from the other signal. The PCB extends into the light-tight housing 157 and into the dust cap 181 to electrically connect the galvanometer to the circuitry of the controller 180.

The controller 180 combines the position signals generated by the

transducers

153, 154 and the sensor signal S generated by the detector 161_nDerived digital position value theta_n、

Packed into a data packet to be transmitted to the main controller 140. As described in more detail below, the data packet includes an identifier T that is the same as the identifier contained in the command that the controller 180 is currently executing. Each data packet including a single set of digital position values theta _n、

But may include the sensor value S_n。

The apparatus further comprises a gas nozzle 120 and an exhaust 121 for generating a gas flow over the build surface (the surface of the powder bed). The gas flow is generated by the pump 111 of the gas recirculation loop 122. The filter assembly 124 filters particles from the recirculated gas that become entrained in the gas flow.

The apparatus further comprises a sensor 190 for generating a signal indicative of the build environment. For example, the sensor may be a sensor as described in WO 2015/040433 and/or WO 2016/0198885, a thermal camera, a visible light camera, or other suitable sensor for additive manufacturing.

Master controller 140 communicates with the following modules of the additive manufacturing apparatus: namely

laser modules

105a, 105b,

optical modules

106a, 106b, build platform 102, dispensing device 108, wiper 109, pump 111, and sensor(s) 150. In this embodiment, the network of modules and controllers 140 is shown as a star network, but other configurations may be used, such as a ring network. The controller 140 controls the modules based on commands in the build file.

As shown in fig. 5, the build file comprises a plurality of commands C to be executed by the controller 140 of the additive manufacturing apparatus ₁To C_n. In FIG. 5, each command C₁To C_nRespectively, including the desired states OA, LA, OB, LB, W, H, S, P of the optics module 106a, laser 105a, optics module 106b, laser 105b, wiper 109, dispensing device 108, build platform 102 and pump 11. Execution of command C by controller 140₁To C_nTo cause the controller 140 to generate signals that cause the module to assume the desired state defined in each command. For example, the signal may cause the

optical modules

106a, 106b, wiper 108, and/or build platform 102 to move to a desired position, cause the dispensing apparatus to dose powder, cause the

lasers

105a, 105b to turn on or off or change the laser power, and/or cause the pump 111 to turn on or off or change the speed.

Each command is associated with an identifier T that identifies the time at which command C is to be executed. In this embodiment, the time is the time from the start of the build (the time at which the first command is executed). The controller 140 includes a clock 141 and uses a clock signal from the clock 141 to determine the time since the start of the build. The controller 140 responds to the identifier T associated therewith₁To T_nIdentified time to execute each command C₁To C_n。

The time resolution and location at which deterministic control is implemented will depend on the arrangement of the additive manufacturing apparatus and the requirements of the deterministic control. The

modules

105a, 105b, 106a, 106b, 102, 108, 111 may have their own local processors (not shown) for interpreting signals from the controller 140 and controlling the

modules

105a, 105b, 106a, 106b, 102, 108, 111 as appropriate. The signals sent by the controller 140 to the modules may include general instructions to be implemented by various means and/or in multiple steps at the

modules

105a, 105b, 106a, 106b, 102, 108, 111. For example, the controller 140 sends instructions to the

optical modules

106a, 106b to expose a defined line (vector) to the laser beam using a series of spot exposures separated by defined spot distances, each exposure being performed for a set exposure time. The local processor of the optical module may execute this instruction by causing appropriate movement of the galvanometer controlling the steerable mirror used to direct the laser beam 118. This may include generating signals for a plurality of time intervals to cause galvanometer movements by a local processor of optical module 105 to achieve a desired dot spacing and exposure time. However, unlike commands executed by controller 140, neither the signals received by optical module 105 from controller 140 nor those received by the galvanometers from the local processor are associated with an identifier that identifies the time at which the command should be executed by the device (optical module or galvanometer). The instructions are executed when received by a device.

In an alternative embodiment, deterministic execution of the commands is performed at the modules rather than by the central controller 140. Each or at least some of the modules may comprise a local processor and a local clock. At the start of the build, the central controller 140 may synchronize the local clock with the master clock 141 of the controller 140. The controller 140 then sends commands to the modules, each command being associated with an identifier that identifies the local time (as determined using the local clock) at which the command was executed by the module. The command may then be queued at the module and executed at the identified time.

The controller 140 also receives sensor data from the sensor(s) and associates the sensor data received at a particular time as determined by the clock 141 with a timestamp. The sensor data may then be correlated with a command that is associated with an identifier of a corresponding time, such that an action being performed by the additive manufacturing device at the time the sensor data was generated may be determined.

The build file is generated at remote computer 130 and sent to controller 140 over a suitable communication link.

The software used for the design build determines the scan path that the

laser beams

118a, 118b are to follow when consolidating the material in the manner described in WO 2014/207454. Once the scan path has been determined, the allocation of the

laser beam

118a, 118b to the scan of the scan path is determined, for example using the method described in WO 2014/199134. In the figure, the scanning of the layers is performed simultaneously with spreading out the powder using the wiper 108a and lowering of the build platform 102, as described in WO 2015/140547. Thus, the timing of the scanning performed by the

laser beams

118a, 118b will depend on the position of the wiper 108 and the set speed of the scanning. Based on the allocation of the

laser beams

118a, 118b to the scan paths and the set scan speed (initial scan parameters), appropriate scan parameters, such as spot distance and exposure time, laser power and spot size, can be determined. Appropriate scan parameters may be determined using a thermal/energy model that considers the energy input into adjacent regions and the amount of cooling between consolidation of adjacent regions to determine the amount of energy to be input into the regions to achieve the desired consolidation (melting).

Commands are then generated from the scan parameters and scan paths, the software determines a time at which each command is executed by the additive manufacturing device to achieve the desired scan during build, and identifies the determined time in an identifier associated with the command, as shown in fig. 4.

Instructions determined by computer 130 may then be uploaded to controller 140 when the user desires to perform the build.

Referring to fig. 6-8, in one embodiment, the controller 140 generates sub-commands SC for the

subsystems

106, 108, 109, 102 when executing the commands at a specified time. The sub-command SC comprises the command(s) to be executed by the subsystem and the identifier T of the command C causing the sub-command to be generated. For a subsystem, the sub-command SC comprises a command to perform a sensor read of one or more sensors present in the subsystem. For example, the laser 105 or optical module 106 includes a sensor for measuring the laser beam power, and the optical module (also) includes

transducers

152, 153 for measuring the position of the galvanometers and a sensor for capturing images and/or other data about the melt pool formed to consolidate the material. The powder dispenser 108 includes: a sensor for measuring the position of the auger or movable plate, which controls the dispensing of powder from the hopper; and/or a sensor for measuring the amount of powder in the hopper. The wiper 109 includes a position encoder for measuring the position of the wiper 109 and/or a metrology sensor (array) for measuring the z-height of solidified material protruding from the powder bed. The z-axis includes a position encoder for measuring the position of the build platform 102. The apparatus may comprise other sensors, such as an acoustic sensor for recording sound/pressure waves generated by the additive build process and/or an oxygen sensor for measuring the oxygen content in the build chamber 101.

Upon receipt of the sub-command, the sub-system immediately executes the sub-command, which for the sub-command comprising the command to make the sensor read, involves recording the sensor value S₁To S_n. The subsystem forms a sensor data packet comprising a sensor value S₁To S_nAnd an identifier T contained in a sub-command causing a sensor value to be captured₁To T_n. As shown in fig. 6, the sensor data packet is sent to the master controller 140.

Referring to fig. 7, a sensor value S₁To S_nAnd other sensor values z, theta from other sensors,

And commands C marked with the same identifier T are packed together into output packets 201 through 204. Based on the relative sensor values z, theta,

Or the desired position contained in command C, the work plane of consolidation, build volume and/or position on the part at the time of capturing sensor values S may be determined.

The position is based on an output θ from the position encoder,

And the measured position z of the build platform 102, the position encoder for measuring the position used to turn the laser beamTo the position of the steering mirror on the working plane. By using the measured position, the position of the consolidation at the time of capturing the sensor values can be determined taking into account the difference between the desired position and the actual position.

The data packets 201 to 204 are output to a visualization device such as computer 130 and the sensor data S is displayed in a two-dimensional or three-dimensional representation in relation to the captured position on the object. The visualized sensor data may be sensor data related to the melt pool formed during consolidation (e.g., as determined from radiation collected by optical module 106 or at least one acoustic sensor), or may be other sensor data that may affect the quality of the object, such as the oxygen content in build chamber 101 as each region of the object is consolidated. This is made possible by the known timing of events occurring during build.

In one embodiment, determining the identifier to be included in command C takes into account delays in the device, such as communication delays and dynamics of the subsystem. The additive manufacturing device may (periodically) undergo a calibration routine in which a delay in the device is determined. For example, the time difference between: between sending a command to the laser 105 and ramping the laser power up to the required power detected by the photodiode; between sending commands to move the steering mirror or focusing optics and measuring movement of the steering mirror and/or focusing optics to a desired position as determined from the output from the position encoder; and/or send commands to drive the platform 102 to a location and measure the movement of the build platform 102 to a desired location. From these time differences, a calibration map or function is generated and used to determine when the master controller 140 should send the sub-command to the subsystem (as determined by the identifier in the command) so that this action is completed at the desired time (there is a time offset between sending the command and the desired time to perform the action). Build preparation software (or other software that converts scan instructions into commands) uses a calibration map or function to generate an identifier for a command.

If the demand data is used to determine a location associated with a sensor value, a calibration map or function may be used to determine the location of the subsystem at the time the sensor value was captured. For example, the calibration map or function may indicate that command C in output packets 201-204 with the previous identifier corresponds to the required location of the subsystem at the time the sensor value was captured. If the location is a measurement location, there is unlikely to be any significant time difference between the sensor values generated by the different electronic sensors.

It will be understood that numerous modifications and variations may be made to the above-described embodiments without departing from the invention as defined in the claims. Rather than defining the time to execute the command from a common build start time, the times for different commands may be set relative to different start (zero) times. For example, a scan command for a particular layer may be set relative to the start time of that layer formation. The control method may be used with other types of additive manufacturing apparatus, for example, other powder or resin bed additive manufacturing apparatus, such as stereolithography.

Claims

1. A method of monitoring an additive manufacturing process in which an object is built in a layer-by-layer manner by directing a laser beam using at least one movable guiding element of a scanner to solidify a selected region of a material bed, the method comprising: recording position values generated by a transducer measuring the position of the at least one movable guide element; recording sensor values produced by a sensor for detecting radiation emitted from the material bed and transmitted to the sensor by a movable guide element of the scanner; and associating each sensor value with a corresponding one of the position values.

2. The method of claim 1, wherein the at least one movable guide element may comprise: a first movable guiding element for guiding the laser beam to a first dimension; and a second movable guiding element for guiding the laser beam to a second dimension substantially perpendicular to the first dimension, the method comprising: recording a first position value produced by a first transducer measuring a position of the first movable guide element; recording a second position value produced by a second transducer measuring the position of the second movable guide element; and associating each sensor value with a corresponding one of the first and second position values.

3. The method of claim 1 or claim 2, wherein the at least one movable directing element is one or more tiltable mirrors and the transducer measures the angular position of one of the one or more tiltable mirrors.

4. The method of claim 1, wherein associating each sensor value with a corresponding one of the location values comprises associating the sensor value and the corresponding one of the location values with a common identifier.

5. The method of claim 4, wherein the common identifier is a time.

6. The method of claim 5, wherein the common identifier is a time associated with a demand signal directing the scanner to move the laser beam to a location on the material bed, and/or a time derived from a clock signal.

7. The method of claim 1, wherein associating each sensor value with a corresponding one of the location values comprises packaging the sensor value and the corresponding one of the locations in a single data packet.

8. The method of claim 1, comprising: positioning the sensor value in the object and/or in an additive manufacturing apparatus based on the measured position of the movable guiding element.

9. The method of claim 8, wherein positioning the sensor values in the object comprises positioning the sensor values in a coordinate reference frame of the object.

10. The method of claim 8, wherein positioning the sensor values in the additive manufacturing apparatus comprises positioning the sensor values in a coordinate reference system of the material bed.

11. The method of claim 1, comprising: the signals from the transducers are shielded from the scanner's demand signals.

12. The method of claim 11, wherein the transducer produces an analog signal and the method includes shielding the analog signal from external noise and/or the demand signal until the analog signal is converted to a digital signal.

13. An additive manufacturing apparatus in which an object is built in a layer-by-layer manner, the additive manufacturing apparatus comprising a scanner comprising: at least one guiding element for guiding a laser beam to solidify a selected region of a material bed; a transducer for measuring the position of the at least one movable guide element; a light path having an output for directing light towards a sensor for detecting radiation emitted from the material bed and transmitted to the output by the movable guiding element; and an interface for outputting from the scanner a position signal generated by the transducer; the additive manufacturing apparatus is arranged to perform the method according to any one of claims 1 to 12.

14. Additive manufacturing apparatus according to claim 13, wherein the at least one movable guide element comprises: a first movable guiding element for guiding the laser beam to a first dimension; a second movable directing element for directing the laser beam to a second dimension substantially perpendicular to the first dimension, and the interface for outputting a first position signal generated by a first transducer and a second position signal generated by a second transducer.

15. An additive manufacturing apparatus according to claim 13 or claim 14, wherein the at least one movable guiding element is one or more tiltable mirrors and the transducer measures the angular position of one of the one or more tiltable mirrors.

16. An additive manufacturing apparatus according to claim 13, wherein the interface shields the position signal from electromagnetic interference generated by a demand signal for controlling the position of the movable guide element.

17. An additive manufacturing apparatus according to claim 16, comprising an output line for the position signal and an input line for the demand signal, and a shield for shielding each of the input and output lines from electromagnetic interference generated by the other of the input and output circuits.

18. An additive manufacturing apparatus according to claim 17, wherein the input lines and the output lines are provided as different layers of a printed circuit board, wherein the input lines and the output lines are separated by a ground plane to shield each of the input lines and the output lines from electromagnetic interference generated by signals in the other of the input lines and the output lines.

19. The additive manufacturing apparatus of claim 13, comprising: processing circuitry for processing the position signal, wherein the transducer produces an analog position signal and the processing circuitry comprises an analog-to-digital converter for converting the analog position signal to a digital position signal, the processing circuitry being housed within a housing for shielding the processing circuitry from external electromagnetic interference.

20. A method of identifying a location of an area captured by a sensor in an object or an additive manufacturing apparatus during an additive manufacturing process in which an object is built in a layer-by-layer manner by directing a laser beam to solidify a selected area of a material bed using at least one movable guiding element of a scanner, the sensor being arranged to detect radiation emitted from the material bed and transmitted to the sensor by the movable guiding element, the method comprising: receiving a sensor value generated by the sensor; receiving position values generated by transducers measuring the position of the at least one movable guide element, each sensor value being associated with a corresponding one of the position values; and for each sensor value, determining a location position in the object and/or the additive manufacturing apparatus of a region from which the sensor value was generated during the additive manufacturing process.

21. The method of claim 20, the method comprising: displaying the sensor values in a multi-dimensional representation with respect to their positioning positions in the object and/or the material bed.

22. A device comprising a processor arranged to perform the method of claim 20 or 21.

23. A data carrier having instructions stored thereon, which when executed by a processor, cause the processor to perform the method of claim 20 or 21.